1. Field of Invention
The present invention relates to a light emitted diode (LED) controller with de-flicker function; particularly, it relates to an LED controller providing de-flicker function by hysteresis control. The present invention also relates to an LED de-flicker circuit, and an LED de-flicker method.
2. Description of Related Art
FIG. 1 shows a schematic diagram of a prior art LED controller 1 for controlling an LED circuit 4 which has at least one LED. The brightness of the LED can be adjusted according to a duty ratio of a pulse width modulation (PWM) signal 2. The higher the duty ratio is, the brighter the LED is. In the circuit shown in FIG. 1, a duty ratio calculation circuit 110 counts the pulse width and the period of the PWM signal 2 by a high frequency clock signal CLK 3, to obtain the duty ratio (expressed by an n-bit digital signal). However, as shown in FIG. 2, the rising and falling edges of the PWM signal 2 often skew in an actual case, and the clock signal CLK 3 might jitter. Either condition can result in an error of the duty ratio calculation. Thus, although the PWM signal 2 remains unchanged, the duty ratio may change because of the error of the duty ratio calculation, and this may cause the LED to flicker.
In view of the foregoing, the present invention provides an LED controller with de-flicker function and an LED de-flicker circuit and an LED de-flicker method, to solve the above flicker problem.